Why are my sprinkles beneath the frosting
Welcome to the Blender community!

All you need to do is continue watching that video until the very end :) BlenderGuru addresses that issue.

Edit: I looked at the file you posted, and the short answer I posted above is incorrect.

The reason why your sprinkles are not showing up properly is that you did not apply the Solidify modifier. BlenderGuru did this at the beginning of Level 1: Part 5.

This is important because of particles are created on the original mesh prior to the other modifiers being applied. You can see that below, where the Solidify modifier is adding additional icing that covers the sprinkles.



To fix this, you'll need to go to the Modifiers tab (the blue wrench) and apply the Solidify modifier. However, when I tried to do this in your file, I received an error due to Multi-user data. This just means that multiple objects have been "linked" together so that if you edit the data for one object, all the objects change.

To fix this, head over to the Object Data Properties tab, which has an icon that looks like a green triangle. Then, press the button labelled "2". The "2" indicates that there are two objects using the data, and pressing it will make this a single-user (unique object).



Once you've done that, head back to the Modifiers tab, and apply the Solidify modifier. The sprinkles will now be showing up on top of the icing, and you should be ready to continue through the Donut tutorials!